Molecular Genetics Exam 2 Flashcards
**The core octamer of a nucleosome is composed of
**
one each of 8 different types of histones
two tetramers of histones H3 and H4
a tetramer of histones H3 and H4, and two dimers of histones H2A and H2B
the linker histone H1
a tetramer of histones H3 and H4, and two dimers of histones H2A and H2B
The site of many post-translational modification of the histone proteins is the
charged tails at the N-terminal end
conserved wing helix folds
charged tails at the C-terminal end
extended histone-fold domain at the C-terminal end
charged tails at the N-terminal end
Brief digestion of eukaryotic chromatin with micrococcal nuclease gives a visible ladder of bands on an agarose gel separated from each other by multiples of ~180 bp. The fragment size represents
the different histone proteins
multiples of single nucleosomal repeat lengths of DNA
DNA that was wrapped around the core histone octamer
linker DNA
multiples of single nucleosomal repeat lengths of DNA
The location of the centromere within a chromosome is determined by
the presence of the histone variant CENP-A.
the presence of linker histone.
the presence of an evolutionarily conserved centromere-determining sequence.
the point of equidistance between the two chromosome ends.
the presence of the histone variant CENP-A.
Heterochromatin is
condensed, transcriptionally active chromatin.
decondensed, transcriptionally silent chromatin.
condensed, transcriptionally silent chromatin.
decondensed, transcriptionally active chromatin.
condensed, transcriptionally silent chromatin.
Which of the following occupies the largest portion of the human genome?
introns
intergenic DNA
protein-coding sequences
gene regulatory sequences
intergenic DNA
Condensation of chromatin requires ATP-hydrolyzing enzymes and to loop DNA and achieve a 10,000 fold packing ratio.
the kinetochore complex
the Ki-67 proteins
the condensin complex
the cohesin complex
the condensin complex
**What statement is not true about plasmid DNA?
**
Plasmid DNA is self-replicating
Most plasmids are small, double-stranded circles.
Plasmid DNA is only found in bacteria
Plasmid DNA is extrachromosomal
Plasmid DNA is only found in bacteria
**Which of the following is true of bacteriophage DNA packaging?
**
Bacteriophages take their host cell’s histone proteins to package their DNA
Bacteriophages usually have a lot of proteins associated with their DNA, helping to package it
Bacteriophages must pack their genome into a nucleus
Bacteriophages must pack their genome into a capsid
Bacteriophages must pack their genome into a capsid
Histone proteins are the main architectural proteins found in bacteria.
True False
False
Mitochondria contain DNA that encodes proteins important for oxidative phosphorylation.
True False
True
**Which of the following statements is correct?
**
DNA polymerase can start synthesis de novo.
There are five types of DNA polymerase in mammalian cells.
DNA polymerase catalyzes the formation of a phosphodiester bond between the first 3′hydroxyl group of the new dNTP and the 5′-phosphate of the last nucleotide in the newly synthesized strand.
DNA polymerase requires a primer to get started.
There is only one type of DNA polymerase in bacterial cells.
DNA polymerase requires a primer to get started.
Which of the following is NOT TRUE with regards to DNA replication?
DNA replication initiation begins at a negatively supercoiled origin of replication
DNA replication is semiconservative
The origin of replication is rich in A and T nucleotides.
DNA replication in bacteria is normally bidirectional
DNA replication on the lagging strand is continuous
DNA replication on the lagging strand is continuous
Which of the following is an enzyme that would be found in Escherichia coli but not in humans?
DNA pol I
PCNA
Mcm2-7
RFC
DNA pol alpha
DNA pol I
What protein or protein complex binds to the origin of replication in E. coli cells to initiate DNA replication?
ORC
Mcm2-7
DnaA
Topoisomerase II
Helicase
DnaA
When does DNA replication occur in a eukaryotic cell?
G2 phase
G1 phase
M phase
S phase
S phase
Which statement is NOT correct?
Eukaryotic chromosomal DNA replication occurs after replication licensing
Eukaryotic chromosomal DNA typically has only one origin of replication
Mammalian origins of replication do not have a consensus sequence
An origin of replication is a site on chromosomal DNA where a bidirectional pair of replication forks initiates.
Eukaryotic chromosomal DNA typically has only one origin of replication
Which enzyme is responsible for sealing the DNA backbone following primer removal?
Restriction endonuclease
DNA ligase
Helicase
RNA polymerase
DNA gyrase
DNA ligase
Which enzyme causes a double-strand DNA break while functioning?
RPA
Topoisomerase I
Klenow fragment
Topoisomerase II
DNA helicase
Clamp loader
Topoisomerase II
Select all of the following that describe DNA transactions during replication.
The main enzyme for replication is DNA polymerase
It is semidiscontinuous
It does not have a specific beginning
It is bidirectional with 2 replication forks
It is conservative
The main enzyme for replication is DNA polymerase
It is semidiscontinuous
It is bidirectional with 2 replication forks
An induced mutation occurs
spontaneously
as a result of interaction of DNA with an outside agent
as a result of natural processes in cells
as a result of DNA replication errors
as a result of interaction of DNA with an outside agent
The most frequent UV light-induced DNA damage is
oxidation of guanine to 8-oxoguanine
double-strand breaks
induction of 5-bromouracil
forming a thymine dimer
forming a thymine dimer
Which of the following is an intercalating agent?
5-bromouracil
8-Oxoguanine
Ethidium bromide
Nitrosamine
Ethidium bromide
Intercalacting agent: compounds that insert themselves between DNA base pairs and damage the DNA
Removal of DNA-protein cross-links will most likely occur using which of the following enzymes?
methyltransferase
SPRTN protease
DNA polymerase IV
DNA photolyase
SPRTN protease
Which repair pathway would probably be involved in specifically recognizing and removing uracil (and other modified bases) from DNA?
non-homologous end joining
homologous recombination
nucleotide excision repair
base excision repair
base excision repair
The XP proteins are important for which type of repair?
direct repair
non-homologous end-joining
nucleotide excision
base excision
nucleotide excision
DNA repair mechanisms exhibit a recurrent theme. Which of the following describes this theme accurately?
A ribosome recognizes the damage, a RNA polymerase translates the DNA sequence, and a DNA polymerase connects double stranded DNA
A polymerase removes DNA damage, a nuclease adds in the correct nucleotides, and a ligase seals double stranded DNA breaks
A nuclease cuts out the damage, a polymerase adds in the correct nucleotides, a ligase fills in the nick in the backbone.
A methyltransferase recognizes DNA damage, a glycosylase cuts the damage out, and a photolyase adds in the correct nucleotides
A nuclease cuts out the damage, a polymerase adds in the correct nucleotides, a ligase fills in the nick in the backbone.
Which type of repair uses DNA glycosylases?
base excision
nucleotide excision
non-homologous end-joining
direct repair
base excision
**The DNA repair system that removes replication errors and requires Mut proteins is
**
Potoreactivation
Nucleotide excision repair
Mismatch repair
Translesion DNA synthesis
Mismatch repair
Xeroderma pigmentosum may be caused by mutation in the gene that encodes DNA polymerase eta (η).
True False
True
DNA polymerase eta (η) repairs DNA damage.
True False
False
**Transcription is defined as the production of a(n):
**
exact complementary strand of RNA from a DNA template.
exact complementary strand of DNA from a RNA template.
strand of DNA with a sequence identical to the RNA template.
strand of RNA with a sequence identical to the DNA template.
exact complementary strand of RNA from a RNA template.
exact complementary strand of RNA from a DNA template.
**Transcription begins at a _sequence encoded by the DNA when ___ recognizes the sequence.
**
origin; DNA polymerase
start codon; ribosome
origin; RNA polymerase
promoter; RNA polymerase
promoter; DNA polymerase
promoter; RNA polymerase
**What is the CORRECT order of transcriptional events that occurs during initiation?
**
Open complex formation, closed complex formation, abortive RNA synthesis, promoter clearance.
Abortive RNA synthesis, open complex formation, closed complex formation, promoter clearance.
Open complex formation, closed complex formation, promoter clearance, abortive RNA synthesis.
Closed complex formation, open complex formation, abortive RNA synthesis, promoter clearance.
Closed complex formation, open complex formation, promoter clearance, abortive RNA synthesis
Closed complex formation, open complex formation, abortive RNA synthesis, promoter clearance.
Which of the following sigma factors is essential for general transcription in exponentially growing E. coli cells?
54
38
70
28
32
70
Which of the following does NOT contribute to the efficiency with which E. coli RNA polymerase binds to a promoter?
The sequence at the +10 region.
The sequence of the upstream promoter element.
The sequence at the -35 region.
The binding of a sigma subunit.
The sequence at the +10 region.
Transcription terminates in E. coli when
the -35 consensus sequence is reached
termination sequences are reached leading to RNA hairpins
pyrophosphorolysis occurs
proofreading has been completed
termination sequences are reached leading to RNA hairpins
*leads to RNA polymerase dissociation
**In E. coli, what is the function of the lac operon? **
It ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment.
It ensures that bacterial cells produce lactose only when no other food sources are available.
It prevents other sugars from being metabolized until all available lactose has been used.
It ensures that a cell produces enzymes involved in lactose metabolism in a constitutive manner.
It ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment.
**In E.coli, what is the most likely thing to happen with the tryptophan operon when there are high levels of tryptophan? **
tryptophan is inactivating the repressor protein
ribosomes are stalling during translation of the attenuator region
the tryptophan operon will continue to be transcribed at relatively high levels
transcription termination is likely
transcription termination is likely
Which mode of action of a transcriptional regulator is exhibited by allolactose binding to the Lac repressor protein?
DNA looping
DNA binding
allosteric modification
cooperative binding
allosteric modification, reduces its affinity for DNA
Transcription and translation are coupled in bacteria.
True False
true, no nuclear membrane to separate the process
Bacteria generally have introns that must be removed from a primary transcript.
True False
False, bacteria do not have introns and splicingin uncommon
Which of the following is NOT a histone
protein that makes up the core octomer?
A. H1
B. H2a
C. H2b
D. H3
E. H4
H1
Heterochromatin is
A. condensed, transcriptionally active
chromatin.
B. condensed, transcriptionally silent
chromatin.
C. decondensed, transcriptionally active
chromatin.
D. decondensed, transcriptionally silent
chromatin
B. condensed, transcriptionally silent chromatin.
Which protein coats chromosomes to prevent them from sticking together during mitosis?
A. Condensin
B. Cohesin
C. Ki-67
D. Kinetochore
C. Ki-67
DNA organization in eukaryotic cells does NOT include
A. 10nm fiber
B. 20nm fiber
C. 30nm fiber
D. Loop domains
B. 20nm fiber
The transfer of genetic material between the nucleus and mitochondria is
A. Impossible
B. Called Vertical Gene Transfer
C. Called Lateral Gene Transfer
D. Called Rolling Circle Gene Transfer
E. Occurring constantly
C. Called Lateral Gene Transfer
Phosphodiester bonds are formed,
connecting the backbones of adjacent Okazaki fragments, by
A. DNA polymerase
B. topoisomerase
C. DNA ligase I
D. telomerase
C. DNA ligase I
Positive supercoils ahead of the replication fork are resolved by cutting both strands of DNA and unwinding the DNA using
A. helicase
B. DNA polymerase/primase
C. PCNA, the sliding clamp
D. Topoisomerase I
E. Topoisomerase II
E. Topoisomerase II
Replication licensing ensures that
A. DNA replication occurs by a semiconservative mechanism.
B. DNA only replicates once per cell cycle.
C. only one origin of replication is active within a cell at a time.
D. DNA replication only occurs during the G2 phase of the cell cycle
B. DNA only replicates once per cell cycle.
DNA polymerase delta and DNA polymerase epsilon have
A.5′ to 3′ polymerase activity only
B.both 5′ to 3′ polymerase activity and 3′
to 5′ exonuclease activity
C.both 3′ to 5′ polymerase activity and 5′ to 3′ exonuclease activity
D.both 3′ to 5′ polymerase activity and 5′ to 3′ polymerase activity
B.both 5′ to 3′ polymerase activity and 3′
to 5′ exonuclease activity
Telomerase is a ribonucleoprotein complex. The RNA component of the complex
A. has reverse transcriptase activity
B. provides structural support only
C. forms a t-loop
D. provides the template for telomere repeat synthesis
D. provides the template for telomere repeat synthesis
A type of mutation that results in multiple adjacent amino acid changes in a polypeptide is probably caused by the following type of mutation:
A. frameshift
B. transversion
C. transition
D. missense
A. frameshift
An induced mutation occurs
A. as a result of natural processes in
cells.
B. as a result of interaction of DNA with an outside agent.
C. spontaneously.
D. as a result of DNA replication errors
B. as a result of interaction of DNA with an outside agent.
Translesion synthesis is mediated by
A. error-prone DNA polymerases
B. replicative DNA polymerases
C. DNA glycosylase
D. DNA photolyase
E. RNA polymerases
A. error-prone DNA polymerases
In the mismatch repair pathway, DNA damage is recognized by
A. RFC and PCNA
B. exonuclease EXO1
C. MSH and MLH/PMS
D. DNA polymerase
E. Ku proteins
C. MSH and MLH/PMS
Repair of a DNA double-strand break by
nonhomologous end-joining is initiated by
A. the endonuclease Artemis.
B. Ku70 and Ku80.
C. DNA polymerase.
D. DNA-dependent protein kinase catalytic subunit
B. Ku70 and Ku80.
One big (and real) difference between origins in eukaryotes and prokaryotes is:
A. a prokaryotic closed circle of DNA usually only has one origin.
B. eukaryotic DNA only has one origin
C. origins are used for transcription in
prokaryotes
D. replication from a specific origin will occur many, many times before a cell divides in
eukaryotes
A. a prokaryotic closed circle of DNA usually only has one origin.
The enzyme used in bacteria to directly fix thymine dimers
A. Glycosylase
B. Ku
C. Photolyase
D. Methyltransferase
E. SPRTN Protease
C. Photolyase
Some mutations are very large and form abnormal chromosomes. An example of this is a mutation that results from a section of DNA being broken away from
the chromosome and attaching to the end of a different chromosome. This is called a(n)
A.deletion mutation
B.duplication mutation
C.inversion mutation
D.translocation mutation
E.abasic mutation
D.translocation mutation
In which level of gene expression control is chromosome position within the nucleus inside of chromosomal territories
A.Level 1
B.Level 2
C.Level 3
D.Level 4
C.Level 3
A transversion mutation is one in which
A. one pyrimidine base is replaced with another, or one purine base with another.
B. one pyrimidine base is replaced with a purine base or vice versa.
C. there is a C to T substitution.
D. there is an A to G substitution
B. one pyrimidine base is replaced with a purine base or vice versa.
Which of the following is the appropriate direction for synthesis of DNA and RNA?
A. 2’ to 5’
B. 3’ to 5’
C. 5’ to 2’
D. 5’ to 3’
E. 5’ to 4
D. 5’ to 3’
Bidirectional replication
A. occurs only in prokayotes
B. occurs only in eukaryotes
C. occurs in both prokaryotes and
eukaryotes
D. only unidirection replication occurs in
prokaryotes and eukaryotes!
C. occurs in both prokaryotes and eukaryotes
Which base deaminates to form uracil?
A. adenosine
B. cytosine
C. thymine
D. guanine
B. cytosine
Which of the following occupies the largest portion of the human genome?
A. protein-coding sequences
B. Introns
C. Repeat sequences
D. Gene regulatory sequences
C. Repeat sequences
